Motor vehicles may provide steering assistance to amplify a force or torque applied by a driver of the vehicle (i.e., at a steering wheel) to the steering assembly of the vehicle. Vehicles, for example, generally have either electric power assisted steering (EPAS) or hydraulic power steering. Vehicles with power steering systems may also be equipped with adaptive steering systems, such as, for example, adaptive front steering (AFS) systems. Adaptive steering systems may, for example, continuously and intelligently alter the relationship between a driver's steering inputs at the steering wheel and the angle of the steered road wheels of the vehicle. An adaptive steering system, for example, varies the degree that the road wheels turn in response to rotation of the steering wheel via a mechatronic auxiliary system (e.g., including an AFS motor).
Adaptive steering systems may, therefore, be used to adjust a rotation angle in the steering assembly in response to a vehicle's operating conditions. For example, an adaptive steering controller may receive data regarding the vehicle's operating conditions and adjust the angle applied by the driver (i.e., the angle provided by the driver at the steering wheel). This adjustment is generally referred to as an overlay angle, and represents the difference between the angle at the steering wheel (i.e., the driver input angle) and the angle of the steered road wheels (i.e., the angle of the rod coupled to the wheels). In this manner, when the AFS system is operational and the AFS motor is powered, the AFS system may estimate the external torque that is applied to the system based on the amount of torque that is needed to generate the desired overlay angle (i.e., the torque applied by the AFS motor).
High torque events (i.e., events producing external torques outside the normal range of torques typically applied by a driver), such as, for example, caused by potholes, during steering catch, or due to reduced steering assist can, however, damage an AFS system. Accordingly, to mitigate damage, AFS systems are often configured to detect high torque events and mechanically lock the AFS motor. However, once the AFS system is locked (and the motor is depowered), the system loses its ability to estimate the external torque, which in turn prevents the system from accurately determining when to unlock once the high torque event is over.
It may, therefore, be advantageous to provide systems and methods that may estimate the amount of torque in an AFS system when the system is locked.